Telephone system.



P. LAVERY & W. E. BANDLOW.

TELEPHONE SYSTEM. APPLICATION FILED 313.24, 191s.

Patented Feb. 3, 1914.

2 SHEETS-SHEET 1.

P. LAVERY & W. E. BANDLOW.

TELEPHONE SYSTEM.

APPLIGATIONEILED 213.24, 1913.

1-,085,6 1 5 Patented Feb. 3, 1914.

2 SHEETSSHBET 2.

gig/anions. in 65565- Wfif cfn c l zow ,By 17 a to vne ys. '6 y?! w COTLUMBXA PLANOGRAPH cd., WASHINGTON, D. c.

rTED s'rn'rns ,PATENT on PHILIP LAVERY, 0F WEBSTER, AND WALTER E. BANDLOW, OF DUDLEY, MASSACHUSETTS.

TELEPHONE SYSTEM.

To all whom it may concern:

Be it known that we, PHILIP LAvERY and WALTER E. BANDLOW, citizens of the United States, residing at Webster and Dudley, respectively, in the county of Worcester and State of Massachusetts, have invented a new and useful Telephone System, of which the following is a specification.

The principal object of this invention is to provide an arrangement by which listening by a third party is prevented on party lines.

The invention also has for its object the provision of means for this purpose of exceedingly simple and inexpensive character and of such a nature that it cannot be tampered with by users under ordinary circumstances. Although this is the chief use of the invention it can be employed anywhere for the purpose of automatically preventing the connection of a third station with a line when two stations are already in connection.

Further objects and advantages of the invention will appear hereinafter.

Reference is to be had to the accompanying drawings in which- 7 Figure 1 is a diagrammatic illustration of 1 three stations on a party line telephone system showing certain details of construction of the mechanism, and Fig. 2 is a similar view of a station for a different system.

The invention is illustrated in Fig. 1 as applied to the parallel or bridge telephone system but it can be used obviously on a series circuit with equal success. The three stations are designated A, B and C in the drawings, the receiver being shown on at station B and ofi at stations A and C. In other words, stations A and C are communicating with each other and the problem is to prevent a person at station B from listening to the conversation.

In order to describe the invention fully I will first describe the connections whereby stations A and C can communicate with each other. The receiver hook 10 controls contact bet-ween springs 11 and 12 and also 12 and 13. When the hook is down as at B the springs 11 and 12 are in contact, and 12 and 13 out of contact. When it is up as at C 12 and 13 are in contact and 11 and 12 out of contact. If it is assumed that all the receivers are on and the operatorat A removes his recelver, a connection Wlll be Specification of Letters Patent.

Patented Feb. 3,1914.

Application filed February 24, 1913. Serial No. 750,236.

made from the positive side of the line through the battery 15 the receiver 16 transmitter l7, springs 13 and 12 to the negative side of the line. This permits the bells in all the other stations to be rung by means of any ordinary push button system generator or the like, the current going from the positive side of the line through the bell 18, the springs 11 and 12 and around to the negative side of the line. N ow if the party at station C, which is supposed to have been called, takes off the receiver, the hook will rise and disconnect the springs 11 and 12 and connect the springs 12 and 13. This results in cutting out the bell and permitting the circuit through the receiver and transmitter to be completed through the battery and the springs 12 and 13 in an obvious manner.

As so far described, the parts are the same as have been used heretofore in telephone systems. The additional features now come into operation. Stations A and C while the conversation is going on, permit a current to flow from the battery through a third circuit comprising a magnet 20 and through a circuit breaker 1A to the negative side of the line. This is a circuit through a high resistance and does not interfere with the talking clrcult for that reason. The same connection of course is made at both stations and the electromagnets 20 are so designed that with the current which they receive in this way they are not sufiicient to attract the a-rmatures 21 from their normal position and the two instruments at A and C are used exactly as if this attachment were not provided. Now, however, let it be as- .sumed that a person at station B takes ofi the receiver and attempts to listen to the 1 conversation. fdinary results incident to a system of this kind, but first it will result in connecting the electromagnet 20 at station E with the This will have all the orline (with all three of the batteries in parallel). This is done by the automatic closing of the circuit breaker 12 when the hook 10 rises. The addition of a third battery to the two already in circuit results in energizing the magnet 20 at station B to such an extent as to cause the armature 21 at that station to be lifted. This armature is guided by vertical guiding posts 22 and is provided with an insulating projection 23 thereon,

preferably consisting of a vertical sheet of mica. On account of the rising of the armature 21 this sheet of mica is brought in between the diverging ends of the two springs 12 and 13 at station B before they come into contact, and prevents the making of the circuit through the receiver and transmitter at that station. Consequently the party at station B cannot overhear the conversation.

As soon as the receiver at station E is hung on the hook, the two springs 12 and 13 are separated mechanically and immediately thereafter the circuit breaker lt at that station is opened and consequently the armature 21 drops. It will be understood of course that the armatures 21 at the other two stations will be attracted by the magnets with equal force but as the two springs 12 and 13 are already in contact, this attraction will simply result in bringing the mica insulating member 23 up against a small projection 130 on the spring 13 at the two stations A and G and the mica can not be forced in between the two springs, thus the two parties originally talking can continue to talk without any interruption. It will be seen, therefore, that a third party cannot by any possibility overhear the con versation and consequently without any material additions to the present equipment of a telephone system, a multiple party line can be practically a private line for all the parties thereon. The utility of this result need. not be explained at length as it will be obvious.

Fig. 2 shows another system of wiring, illustrating how this invention can be applied thereto. The numbers 1O, 14, 15, 16, 17 and 18 represent the same elements as in Fig. 1. The numbers 11*, 12, 13, 13 20 21 correspond to those in Fig. 1 having the same numbers without exponents. In addition a generator 30 is shown to ring the call bells 18 at the several stations, also a primary coil 31 and secondary 32 constituting an induction coil for long distance use. In this case also the mica insulator 23 works horizontally or nearly so, being mounted on the end of a rod 34 slidable in bearings 35 in a metal frame 36. A spring 37 is shown attached to the armature and to an adjusting rod 38 to permit the tension to be ad justed. In this case the contact 12 is in direct connection with one of the main lines which we will call the plus line. It is normally held by the receiver (acting on a pivoted lever 100) in the dotted line position and the bell circuit is completed from it through the contact 13 bell l8 and generator 30 to the other line. When the receiver is removed the lever raises the contact spring 12 so as to bring 12*, 11 and 13 into contact. Now connection is made from the line through 12*, 11 and 13 15, 17, 31, 32, and 16 to the other side of the shown it as applied to a particular type of telephone instrument and to a parallel system, we are aware that the invention can be carried out in many other ways and applied to other types of instruments and electrical systems, and that it can be applied to any one or more stations of a system without departing from the scope of the invention as expressed in the claims.

We claim 1. In a telephone system, the combination with the bell and talking circuits at each station, of an electromagnet bridging the line, an armature for the electromagnet movable toward and from the core thereof, and an insulating member on the armature for moving between contacts of a talking circuit when the armature is attracted into contact with the core of the magnet and holding said talking circuit open.

2. In a telephone system, the combination with the transmitter and receiver circuit, of an electromagnet at each station connected with the line, means operated thereby for holding the transmitter and receiver circuit at one station open when all the magnets of the system are energized, receiver hooks at the stations, and means operated by areceiver hook for disconnecting the electromagnet at that station only from the line when that receiver hook is down.

3. In an electrical system, the combination of a pair of conducting members adapted to come into contact, an electromagnet, a movable armature for the magnet, insulating means on the armature in position to move between said members when the armature moves to keep them out of'contact, a receiver hook, and means independent of said conducting members operated by the receiver hook for deenergizing the electromagnet when the hook is down. 1

4.. In a telephone system, the combination with the transmitter and receiverv circuit, of an electromagnet arranged in parallel with said circuit at each station, means at each station adapted to be operated by the electromagnet for holdingopen the transmitter and receiver circuit at that station, said circuit having a pair of contacts, said means comprising an armature movable by said two other stations, and an insulating member movable with said armature between said contacts to hold them apart.

5. In a telephone system, the combination with the bell and talking circuits at each station, of an electromagnet bridging the line at each station, an armature for each electromagnet, a pair of springs adapted to come into contact with each other for completing the talking circuit at each station and a sheet of insulating material on said armature adapted to come between said springs when the armature is attracted to the magnet.

6. In a telephone system, the combination with the bell and talking circuits at each station, of an electromagnet bridging the line at each station, an armature for each electromagnet, a pair of springs adapted to come into contact with each other for completing the talking circuit at each station, a sheet of insulating material on said armature adapted to come between said springs when the armature is attracted to the magnet for the purpose of holding open the talking circuit, a receiver hook at each station arranged to permit said springs to come into contact when the receiver is taken oil, and a circuit breaker in series with said electromagnet adapted to keep the electromagnet circuit open when the hook is down and to close it when the hook is up.

7. In an electrical system, the combination with a pair of line terminals, of a circuit connected with said terminals, a battery in said circuit, a circuit from the battery to one of the line terminals, and means operated by the last named circuit for holding open the first named circuit.

In testimony whereof we have hereunto set our hands, in the presence of two subscribing witnesses.

PHILIP LAVERY. WALTER E. BANDLOW.

Witnesses:

I JAMES E. GREELEY,

ARCHER R. GREELEY.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents. Washington, D. 0. 

